An image scanner is a device that optically scans a printed document or object and converts it into a digital image. In most flatbed-type scanners, the document is placed, face down, on a glass platen. An opaque lid or cover of the scanner is then lowered over the document to block ambient light, effectively sandwiching the document between the glass platen and the cover. Underneath the platen is a light source that illuminates the document and a sensor that senses the intensity and color of light reflected by the document. The document is then recreated in digital form from the intensity and color information.